Process for obtaining polymers of ethylene and cycloolefins

Abstract

A terpolymer containing: a) from 90% to 50% by weight; preferably from 90% to 70% by weight of ethylene derived units; b) from 5% to 40% by weight; preferably from 5% to 20% by weight of derived units of alpha olefin of formula CH 2 ═CHA wherein A is a C 1 -C 20 alkyl radical; c) from 2% to 30% by weight, preferably from 5% to 20% by weight of cycloolefins derived units. Said terpolymer being characterized by the following features i) distribution of molecular weight Mw/Mn lower than 3.5; preferably lower than 3; more preferably lower than 2.7 ii) solubility in xylene at 25° C. higher than 99%.

1. A process for polymerizing ethylene, alpha olefins of formula CH 2 ═CHA wherein A is a C 1 -C 20  alkyl radical, and at least one cycloolefin to form a terpolymer, the process comprising the step of contacting under polymerization conditions ethylene, the at least one alpha olefin of formula CH 2 ═CHA and the at least one cycloolefin in the presence of a catalyst system obtained by contacting:
 a) a compound of formula (I): 
 
       
         
           
           
               
               
           
         
         
           wherein
 M is chromium; 
 X, equal to or different from each other, is a hydrogen atom, a halogen atom, a R, OR, OSO 2 CF 3 , OCOR, SR, NR 2  or PR 2  group wherein R is a linear or branched, cyclic or acyclic, C 1 -C 40 -alkyl, C 2 -C 40  alkenyl, C 2 -C 40  alkynyl, C 6 -C 40 -aryl, C 7 -C 40 -alkylaryl or C 7 -C 40 -arylalkyl radical; optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two X groups can be joined together to form a group OR′O wherein R′ is a C 1 -C 20 -alkylidene, C 6 -C 20 -arylidene, C 7 -C 20 -alkylarylidene, or C 7 -C 20 -arylalkylidene radical; 
 Z is a divalent bridging group selected from C 1 -C 20  alkylidene, C 3 -C 20  cycloalkylidene, C 6 -C 20  arylidene, C 7 -C 20  alkylarylidene, or a C 7 -C 20  arylalkylidene radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, or it is a silylidene radical containing up to 5 silicon atoms; Z can also be an aliphatic or aromatic ring condensed with T 2 ; 
 R 1 , R 2 , R 3 , R 4  and R 5 , equal to or different from each other, are hydrogen atoms or C 1 -C 40  hydrocarbon radicals optionally containing silicon atoms, germanium atoms or heteroatoms belonging to groups 15-16 of the Periodic Table of the Elements or two groups among R 1 , R 2 , R 3 , R 4  and R 5  can also be joined to form a from 4 to 7 membered ring, that can be aliphatic or aromatic and can contain silicon atoms, Germanium atoms or heteroatoms belonging to groups 15-16 of the Periodic Table of the Elements; said ring can contain at least one C 1 -C 10  hydrocarbon radical as substituents; 
 T 1  is a C 6 -C 20 -aryl radical that can be substituted with at least one C 1 -C 20  hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; 
 T 2  is a radical comprising at least one uncharged donor containing at least one atom of group 15 or 16 of the Periodic Table; and 
 
         
         b) an alumoxane or a compound that forms an alkyl cromocene cation,
 the terpolymer comprising:
 1) from 90% to 50% by weight of ethylene derived units; 
 2) from 5% to 40% by weight of derived units of alpha olefin of formula CH 2 ═CHA wherein A is a C 1 -C 20  alkyl radical; and 
 3) from 2% to 30% by weight of cycloolefin derived units, 
 
 and having
 (i) a distribution of molecular weight Mw/Mn lower than 3.5; 
 (ii) a solubility in xylene at 25° C. higher than 99%; and 
 (iii) a melting point (Tm2) of the polymer that fulfils the following relation:
     Tm 2<−2.7 C+ 104,
 
 
  wherein C is the sum of the concentrations of alpha olefins and cycloolefins given by weight; and 
 iv) a glass transition temperature (Tg) of the polymer that fulfils the following relation:
     Tg>− 3.3( C   4 *0.34 +C   c *0.71)+19 
 
 
 wherein C 4  is the concentration of alpha olefins and C c  is the concentration of cycloolefins given by weight. 
 
       
     
     
       2. The process according to  claim 1  wherein T 1  is a phenyl radical or a naphtyl radical that is substituted with at least one C 1 -C 20  hydrocarbon radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements. 
     
     
       3. The process according to  claim 1  wherein in the compound of formula (I), T 2  has formula (IIa or (IIb); 
       
         
           
           
               
               
           
         
         wherein the asterisk (*) marks the position in which the bridge Z is bound, when the bridge Z is a condensed saturated or unsaturated ring the other position in which Z is bound is the position vicinal to the position marked with the asterisk (*); A is a C(R 7 ) group or a T 3  atom, wherein R 7  equal to or different from each other, are hydrogen atoms or linear or branched, saturated or unsaturated C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two R 7  can also be joined to form a from 4 to 7 membered ring; T 3  is a nitrogen or a phosphorous atom; T 4  is sulphur, an oxygen atom, or a NR 7  group; with the proviso that not more than two A groups are T 3  groups. 
       
     
     
       4. The process according to  claim 1  wherein the cycloolefin has general formula (III): 
       
         
           
           
               
               
           
         
         wherein R 1 , R 2 , R 3  and R 4 , independently from one another, are hydrogen atoms, C 1 -C 20  alkyl, C 3 -C 12  cycloalkyl or C 6 -C 18  aryl, or two of R 1 , R 2 , R 3  and R 4 , together with the carbon atom(s) to which they are bound form at least one saturated, partially unsaturated or aromatic ring that bears C 1 -C 20  hydrocarbon substituents. 
       
     
     
       5. The process according to  claim 1  wherein the alpha-olefins of formula CH 2 ═CHA are selected from the group consisting of propylene, 1-butene, 1-hexene, 1-octene and 4-methyl-1-pentene. 
     
     
       6. The process of  claim 4  wherein R 1 , R 2 , R 3  and R 4 , are hydrogen atoms, C 1 -C 8  alkyl, C 3 -C 8  cycloalkyl or C 6 -C 12  aryl. 
     
     
       7. The process of  claim 5  wherein the alpha olefins are selected from the group consisting of 1-butene and 1-hexene. 
     
     
       8. The process of  claim 5  wherein the alpha-olefin of formula CH 2 ═CHA is 1-butene.